1. Field of the Invention
The present invention relates to an improved method of producing a container or the like by deep-drawing a flat blank of a sheetlike aluminium material and to an apparatus for deep-drawing a flat blank of an aluminium metal sheet into an aluminium container or the like.
2. Description of the Prior Art
These are known several techniques of deep-drawing in the art, by means of which drawing ratios of .beta.=2 can be achieved by one single working stroke of the press. Such known techniques are for instance the Auble process (multistep process), the simultaneous system (compound process), the inversion deep-drawing process and the sequential deep-drawing process.
All of these known processes or methods, respectively, are bestowed a common drawback in that the drawing tool necessary for carrying out any said processes demand the installation of presses incorporating extremely large strokes, which demand originates from the prevalence of two sequentially carried out process steps.
For instance, the production or shaping, respectively, of a can having a depth of 70 mm calls for a minimal stroke of the press at the first drawing stroke of 60 mm, at the second drawing stroke a press stroke of 70 mm, for the opening of the drawing tool and subsequent ejection of the can produced 100 mm, thus total 230 mm. Now, deep-drawing presses for the production of aluminium cans and the like commonly available on the market feature in general a stroke of 140-220 mm. Therefore, it is not possible to mount tools or such presses which are necessary for producing cans with a depth of 70 mm. Conclusively, it is necessary to install a custom-made press of special design which however from the viewpoint of capital investment and power consumption is not attractive.
A further drawback is the fact that due to the large or high, respectively, stroke necessary for the production of such deep cans the relative plunger or ram speed is extremely high, following in the deep-drawing tool being heavily stressed which leads to a considerable reduction of its usable service life.
Furthermore, the commonly known inversion deep-drawing process involves a bending of the material being drawn through an angle of 180.degree.. Considering an aluminium sheet coated with varnish such large bending angle involves that the varnish coating is subject to injury.